MS student Yaokun Shi with Advisor K. Haran

This research, funded by the Grainger CEME, discusses changes and advances in a portable MRI device. While maintaining the rotational spatial encodings as embedded gradients in the base magnetic field, the cylindrical magnets have been replaced by an array of cubic magnets to increase the field-of-view of the imaging volume. A new set of 3D-printed structures is manufactured and integrated with motors that have more precise steps at 1.8 degrees per rotation. This allows an increased number of field maps to be generated, producing much better image qualities. A new radio frequency (RF) controller based on a field-programmable gate array is used to drive the custom-made transmitter, and receiver coils wound with copper/litz wire at various gauges and are currently under test. The prototype is shown in Figure 1.

Figure 2. Hand-held MRI prototype.

The pulse sequence used in driving the RF coils has also been designed following a simple free-induction-decay scheme. Using simulated field maps, some sample output images have been generated. A better peak signal-to-noise ratio was observed in images that utilized more field maps, as seen in Figure 2.

Figure 2. Simulated input (left) and reconstructed output (right) images with proton density and T2* weightings. The images were reconstructed based on simulated field maps.

The next step is to finish testing the custom RF coils and integrating all the components to create the very first phantom image scan. Then, potential enhancements would be investigated, including parallel transmitting/receiving for scan-time reduction, custom motors for decreased size and weight cost, and machine-learning techniques to further improve image quality.